Trail Maintainer Tip #1 - The Fall Line Issue

We do not have to look too hard to find the media flashing photos and videos of mountain bikers flying straight down a mountain. While many of us entertain the thought of doing this ourselves, a trail designed to do this is more than likely not a sustainable trail, and ultimately not ideal in most public lands that are maintained by volunteers. There is no doubt that it is much easier to fire up volunteers to build a re-route, than to repair an eroded fall line trail over and over again.

So what is fall line? Fall line is the shortest route traveling downhill, the same path that water flows. Trail users, gravity and water can erode trails, but if water is allowed to channel, this process is accelerated. I recall racing in West Virginia at a muddy ski area and followed the line of water down a trail and discovered the fastest line. While racers were slowed in mud trying to avoid the rocks and water, I flew right through on a firm eroded rock surface hidden beneath a path of water. I experienced first hand where the water went and what it could do to strip all the soil away. I may have won my race that day, but the life lesson on water was my most enlightening and vivid prize.

Building a sustainable trail that resists erosion can be done through proper design, construction and maintenance. I read in Dirt Rag that Jusitn Vander Pol, who is a long time rider, trail builder and maintainer in wet Seattle’s Tokul Creek Trails said “good trail building is 70% good routing”. Vander Pol takes pride in designing trails that drain and dry quickly in an extremely wet climate.

Ultimately, when routing a trail, the trail should be placed across the fall line with an approximate 5% out sloped tread to let the water sheet off the trail quickly before traveling down the trail. To determine maximum trail grade we use the half rule: trail grade should not exceed half the side slope. That rule is a pretty solid rule for keeping trails out of the fall line. Sometimes the rule can be stretched a bit on solid rock or with rock armoring, but if you are a trail designer, that rule should be at the front of your mind.

When choosing a route Art and I look for many things to make what we feel is the best trail. It is not just about going from A to B and adding cool technical features. Besides wanting riders to really enjoy riding the trail, we want the trail to last and be there years down the road. Some of the things we look for when planning a route: keeping the trail grade below half of the slope grade, places to add dips or grade reversals, interesting features (either for technical riding or nature enjoyment) and natural chokes to keep riders on the trail. End result: we have come to learn that some pretty amazing and sustainable trails can be built without aligning them in the fall line. When planning to build a trail, don't let yourself get sucked into the fall line lie.


before

after

Dirty Thursdays 6/21 - 7/5

During the last few weeks Dirty Thursday crews have moved back onto the yellow trail to address some touch-ups to eroding areas and some minor re-routes to fall line sections.

The most recent re-route was originally to be placed across a grassy 20% side slope to the east of the trail, which was in a 35% fall line. As Art and I were laying out a turn for pin flagging, Art noticed we had drifted too close to another trail in this narrow corridor. Art quickly looked for another option on the other side of the trail which was much more rocky. Although there was a tad more work needed on the other side, the result was fantastic, as the trail now passes through areas of glacial erratics, ferns and rock features.

One thing that Art and I have learned is to keep an open mind with the route. Sometimes a trail designer can find what they think is the holy grail of routes, but one small part of that route is not right in design. Many times we have had to abandon our plan and rethink options, until we find a better solution. The final result has always been better than the first plan. This is why taking our time with planning is very important for us. After spending most of our trail building years maintaining poorly designed trails, we have developed a greater appreciation for a well designed trail.






volunteers: Manny and Jeff that braved the heat to work

After last nights build, I rode out of the woods as the sun set to my west. What was a very hot day, was now surprisingly comfortable in the the shade of the woods with the occasional gentle breeze. As I rode down the final trail before reaching the lot, my shoes bouncing back and forth tied to my pack, the sun washed the woods orange leaving only my shadow in front of me. I felt thankful to be riding my bike, a little sweaty, covered in dirt, and there at that exact moment.

-Ellen